Digibind

CLINICAL PHARMACOLOGY

After intravenous injection of Digoxin Immune Fab (Ovine) in the baboon, digoxin-specific
Fab fragments are excreted in the urine with a biological half-life of about
9 to 13 hours.1 In humans with normal renal function, the half-life
appears to be 15 to 20 hours.2 Experimental studies in animals indicate
that these antibody fragments have a large volume of distribution in the extracellular
space, unlike whole antibody which distributes in a space only about twice the
plasma volume.1 Ordinarily, following administration of DIGIBIND (digoxin immune fab) ,
improvement in signs and symptoms of digitalis intoxication begins within one-half
hour or less.2,3,4,5

The affinity of DIGIBIND (digoxin immune fab) for digoxin is in the range of 109 to 1011
M-1, which is greater than the affinity of digoxin for (sodium, potassium)
ATPase, the presumed receptor for its toxic effects. The affinity of DIGIBIND (digoxin immune fab)
for digitoxin is about 108 to 109 M-1.

DIGIBIND (digoxin immune fab) binds molecules of digoxin, making them unavailable for binding at
their site of action on cells in the body. The Fab fragment-digoxin complex
accumulates in the blood, from which it is excreted by the kidney. The net effect
is to shift the equilibrium away from binding of digoxin to its receptors in
the body, thereby reversing its effects.